An optical communication system that uses a wavelength division multiplexing (WDM) scheme of multiplexing optical signals of different wavelengths is known.
Such an optical communication system can configure a complex topology such as a ring interconnection and a mesh by using an optical add/drop multiplexer (OADM) that realizes adding/dropping and path switching of an optical signal for each wavelength.
Moreover, in the optical communication system, the bit rate of multiplexed optical signals is increasing and diversified optical signal modulation schemes are used. Thus, in order to cope with the increasing bit rate and the diversified modulation schemes, a method of flexibly allocating a wavelength bandwidth according to the bit rate and a modulation scheme of an optical signal.
In an optical communication system in which such a method is applied, in order to improve the utilization efficiency of the wavelength bandwidth, rearrangement of allocated wavelengths, switching of wavelength paths, and the like are performed frequently. Thus, it is necessary to change the allocated wavelength and path of a wavelength path in service. Here, the wavelength path means a communication path between two points connected by an optical signal of each wavelength.
For example, Japanese Laid-open Patent Publication No. 2009-147416 proposes a method of preventing a deterioration of signal quality after a path is switched in the 1+1 protection scheme by setting a wavelength dispersion compensation amount in a present optical path to be the same as a wavelength dispersion compensation amount in a reserve optical path in advance or setting a residual dispersion amount to zero.